Periodic inspection maintenance policy with a general repair for multi-state systems

This paper proposes a periodic inspection maintenance model for a system with several multi-state components over a finite time horizons. The system is failed if its performance rate, which depends on the components´ states and the system configuration, is unacceptable. Components in the system are subject to hidden failures which can be found and fixed only at inspections. A preventive repair action is performed after the inspection if the system performance rate falls below the threshold level L. Since the maintenance effect, such as minimal, imperfect or the worse repair, depends on the type and degree of the repair performed on the system, a general model is introduced to denote the different maintenance effect of the multi-state system. The whole system is replaced at T which is given fixed as the system design life or the life expectancy. Particle swarm optimization(PSO) is used to optimize the maintenance threshold L and inspection intervals τ to minimize the maintenance cost rate. A numerical example of a multi-state system are presented to illustrate the use of the proposed model at last.